I built a pay calculator and I'm keen for you to pick it apart

Full disclosure up front: I made this, so feel free to be sceptical. I run OzFinn (a few free AU finance tools) and just shipped a pay calculator: https://ozfinn.com.au/pay

The market's well covered by PayCalculator .com.au and Moneysmart, so I only bothered building it because I wanted three things they don't do:

1. Every input is encoded in the URL, so a result is a single copy-paste. e.g. https://ozfinn.com.au/pay/110000 opens to that exact salary, pay cycle and tax year. Handy for sending HR an offer check or settling a take-home debate.

2. A marginal-bracket breakdown that also spells out your effective rate. On the median full-time salary ($90,500), your *income tax* effective rate is ~21.8% even though your top dollar is taxed at 30%. People consistently overestimate this, and seeing it laid out tends to be the moment the bracket system clicks.

3. A rough wealth projection: it shows what investing 5/10/15% of your take-home pay could compound to over 20 years (nominal, adjustable growth rate, purely illustrative).

What I'm actually after: where's it wrong or misleading, and what's the one feature that would make you reach for it over what you already use? HECS, second jobs and the levy surcharge are the edges I'm least sure I've framed well.